feat: AI commit message generation

[erishforG]

Vision (v1.0: AI agent Git interface)

Auto-generate commit messages by analyzing staged changes.

Proposal

parsec commit [ticket]          # AI generates commit message from diff
parsec commit --conventional    # force Conventional Commits format

• Auto-prefix with ticket number when run inside a worktree
• Shares [ai] config section with feat: AI-generated PR descriptions (OpenAI/Anthropic/Ollama) #242

Reference

GitButler: AI commit messages (OpenAI/Anthropic/Ollama/LM Studio)

Milestone

v1.0